What is the purpose of a junction table in a database?

The purpose of a junction table in a database is to facilitate the linking of two tables that have a many-to-many relationship. In relational database design, when two entities need to be related to each other multiple times, a junction table serves as an intermediary that holds the relationships between them. Each record in the junction table typically contains the primary keys from both tables, essentially creating a composite primary key that uniquely identifies the relationship between entities.

For instance, consider a scenario where you have two tables: one for students and another for courses. A student can enroll in multiple courses, and a course can have multiple students. To effectively represent this relationship, a junction table is created to hold the enrollment data, with foreign keys referencing the student and course tables. This design allows for the management and maintenance of the many-to-many associations efficiently.

While the other options touch on related concepts, they do not define the specific role of a junction table. Storing primary keys is part of the function, but it does not encompass the overall purpose of establishing relationships. Optimizing query performance and enforcing data integrity are broader functions that can be improved through good database design but are not specific to junction tables.